Modern business and graphic needs require reproduction and printing of specific colors in prints produced. For example, business entities increasingly use specific colors to act as identifiers. Specified colors on prints produced by full color electrophotographic printing machines are well known. In fact, faithful color reproduction in full color machines has become essential, as failure of such faithful reproduction of color is extremely noticeable and degrades the utility of the device.
As is well known in the art of printers such as those employing xerographic principles of operation, an electrostatic latent image is formed on a surface and is developed by passing triboelectrically charged developer material or toner proximate the surface so that charged developer material is retained on the surface according to the charge level of the latent image. In the devices of the type to which this invention relates, the latent image on the charge retentive surface formed has three (and often more) distinct levels of charge thereon. The art of xerography has advanced so that multicolor images can be developed and processed substantially concurrently, and these devices take two generalized forms, full process color and highlight colors.
Generally, full process color electrophotographic printers expose a series of images which are separately developed at either separate times and/or at different places. In any event, the separate images are merged to form a composite developed image. Customization of colors used in such devices has involved signal processing techniques in the processing of signals which are used to generate the latent images which form the composite image so that the final composite image has the desired or customized color.
Highlight color printing machines generally operate either by exposing a single image which has varying charge levels therein to develop different colors or by similar methods to full process color machines where images are merged to form a composite image. However, in highlight color devices, which do not provide full process color, customized colors have heretofore been provided in some cases by or with the provision of such color developer material. That is, the enablement of users of devices for developing electrostatic images on charge retentive surfaces in a user desired color in these devices was through the use of developer material which was of the desired color. Other techniques such as gray scaling methods have also been used to obtain results which provide a differentiation in the colors of the images produced such as that disclosed in U.S. Pat. No. 4,903,048. Multi-level highlight color printing machines of the type described in U.S. Pat. No. 4,731,634 to Stark permit the overlapping of certain developer materials to achieve a blended color of two developer materials using a highlight color printing machine also of the type to which this invention relates.
Customized colors specified by the users have been a major concern both of marketers and manufacturers of electrophotographic printers, as users thereof have demanded them. Various methods, as described above, as well as others have been employed to achieve such results. However, these methods and the apparatus used to practice these methods have not always been entirely successful, reliable, or relatively inexpensive. Thus, there exists a need for a relatively inexpensive and simple method and means for operators of electrophotographic printing machines to achieve customization of colors.
The following patents may disclose pertinent information relating to the present invention:
U.S. Pat. No. 4,731,634 PA1 Patentee: Stark PA1 Issued: Mar. 15, 1988 PA1 U.S. Pat. No. 4,078,929 PA1 Patentee: Gundlach PA1 Issued: Mar. 14, 1978 PA1 U.S. Pat. No. 4,903,048 PA1 Patentee: Harrington PA1 Issued: Feb. 20, 1990 PA1 U.S. Pat. No. 4,992,828 PA1 Patentee: Liston PA1 Issued: Feb. 12, 1991 PA1 U.S. Pat. No. 4,853,738 PA1 Patentee: Rushing PA1 Issued: Aug. 1, 1989 PA1 U.S. Pat. No. 4,998,144 PA1 Patentee: Karn PA1 Issued: Mar. 5, 1991 PA1 Japanese Application No. 63-254469 PA1 Applicant: Nakamura PA1 Published: Oct. 21, 1988
The relevant portions of the foregoing disclosures may be briefly summarized as follows:
U.S. Pat. No. 4,731,634 to Stark is incorporated herein by reference. This patent discloses a method and apparatus rendering latent electrostatic images visible using multiple colors of dye toner or developer through a single pass system.
U.S. Pat. No. 4,078,929 to Gundlach discloses an apparatus for rendering tri-level electrostatic images visible using plural colors of developer material through a single pass system.
U.S. Pat. No. 4,903,048 to Harrington discloses a method for arranging pixels of two colors produced by a highlight color printer to enable apparent shading of produced images on a third color substrate.
U.S. Pat. No. 4,992,828 to Liston discloses a method for changing the input to the controller to change the output imaging through use of a digitizer to select certain areas of the output document to be specially edited.
U.S. Pat. No. 4,853,738 to Rushing discloses an apparatus for automatic setup and/or maintenance of process control parameters. In this manner, it provides for a system which is automated to produce images with good color, balance, fidelity and tonal reproduction. The patent is primarily directed to controlling process parameters and adjustments thereof to provide color and density shifts at various known averages of human visual sensitivities to density and color shifts at a variety of levels.
U.S. Pat. No. 4,998,144 to Karn discloses a color copier which receives a color palate representing the plurality of colors flexible by an operator to produce reproductions. The color is selected by a series of electrical data pulses which is stored and can be compiled by the central processing unit to the image forming apparatus during any copying procedure.
Japanese Laid open application No. 63-254469 discloses a bar coding of colors available for copying. The operator selects the combination of colors to be adjusted from a bar coded chart and transfers the data to the copier by reading or tracing the bar code for such color. Thus, the selected colors can be executed exactly.
Thus, there has been a need and desire for users of color, both highlight color printers and reproducers of documents, for a device which produce specified and repeatable colors as desired. For example, the most important case may be where a company's logo or trademark is used and needs to be used in both a color and size format, as appropriately designated by corporate standards. Further, there are many other documents where both colors shading and tinting serve as identifiers and informational sources as well as providing pictorially appropriate images and senses. Thus, whenever such documents are created electronically, there is a need to identify and assign not only colors to these documents but to the particular portions of the documents. While such assignment procedures and rules are well known parts of electronics in document creation, the identification procedure of the exact color shade desired and user selection is not obvious and its combination with such procedure and enablers has been needed.
According to one aspect of the present invention, there is provided an electrophotographic printing machine of the type having a photoconductive surface on which a developed image is formed for producing a plural color image on a sheet substrate. This printing machine comprises means for forming a developed image on the photoconductive surface by attracting a plurality of developer materials to the photoconductive surface with each developer material being of a different color, means for adjusting the forming means so as to change the quantity of one of the plurality of developer materials attracted to the photoconductive surface so as to vary the relative quantity of the developer materials producing the developed image, and means, responsive to the adjusting means, for storing electronic signals corresponding to selected adjustments of the adjusting means. The adjusting means may comprise a user interface responsive to user command signals for adjusting said forming means, and the forming means may comprise an image generating means for recording a latent image on the photoconductive surface, which can include a raster output scanner for generating multiple output levels, said adjusting means being coupled to said raster output scanner, to adjust the relative output levels of said raster output scanner. The forming means can also include image developing means for developing the latent image recorded on the photoconductive surface, which can include a plurality of developer units with each developer unit having different color developer material. The developer units of this aspect of the invention can also be electrically biased to various levels, said adjusting means adjusting the relative bias levels on said developer units so as to adjust the attractive force between the developer material in said developer unit and the latent image. The forming means may also further include means for charging the photoconductive surface wherein the adjusting means adjust the charging means so as to change the level of charge applied to the surface by the charging means.
According to another aspect of the invention, there is provided a method of printing sheets having user customized colors in an electrophotographic printing machine including a photoconductive member. The method comprising the steps of: forming a developed image on the photoconductive member by attracting a plurality of developer material to the photoconductive member with each developer material being of a different color, adjusting an apparatus employed in said forming step so as to change the quantity of one of the plurality of developer materials attracted to the photoconductive member so as to vary the color of the image produced on the sheets, storing electronic signals corresponding to selected adjustments made to the apparatus in the adjusting step; and applying subsequently selected signals stored in said storing step to the apparatus so that selected colors are replicable. The forming step can also include imaging the photoconductive member with a raster output scanner having plural output levels to form a plural level latent image and wherein said adjusting step comprises varying the relative output levels of the raster output scanner and/or developing the latent image with developer material of a plurality of colors from an electrically biased developer housings. The forming step can also comprise imaging the photoconductive member with a ROS having plural output levels to form a plural level latent image and wherein said adjusting step comprises varying the relative output levels of the ROS.
According to yet another aspect of the invention, there is provided a color printer for printing copies in operator selected colors, which comprises an image forming means for image-wise exposing a insulative surface to record a latent image thereon having a plurality of differing potential levels thereon, a plurality of electrically biased developer units for housing and delivering electrically charged developer material of a plurality of colors to develop the latent image recorded on the photoconductive insulative surface, an operator interface including means for selectively adjusting the relative bias levels on the developer units and means for selectively adjusting the image forming means to vary the relative differences in the potential levels of the latent image, and memory means for storing a series of electrical data signals representing the electrical bias and the potential levels for subsequent reuse.
While the present invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.